Im not sure its "email", but no reinstall does nothing. Its some messaging interface that responds to a voice command to send a hangouts message to some contact. If you do a voice command in google now to send a hangouts message to someone it doesn't know to use hangouts or touchdown and has you pick. Somehow Android Auto uses the same stuff, but incorrectly picks touchdown and opens a new email in touchdown with whatever command is sent. Somehow you guus are tied into the same messaging interface hangouts is supposed to be a lone app on.